1. Field of the Invention
This invention relates to a photosensitive material useful for forming a fine pattern in the manufacture of a semiconductor device and the like.
2. Description of the Related Art
In the manufacture of electronic parts such as a semiconductor element, a fine pattern is formed by way of a photolithography. This technique of photolithography is performed as follows. Namely, a photoresist thin film is first formed by coating a resist material onto a semiconductor substrate for example. The photoresist thin film thus formed is then exposed to light through a prescribed mask pattern, and subsequently subjected to various processes such as development and rinsing, thereby forming a resist pattern. This resist pattern is then utilized as an etch resistant mask in an etch process, and the exposed portions of the substrate are etched to form a pattern of fine line or window thereby obtaining a desired pattern. Finally, the resist pattern remaining on the substrate is removed, thereby obtaining a thin film pattern.
In view of a trend in recent years toward further increasing the integration of semiconductor elements, there has been demanded the development of a photolithographic technique which is capable of realizing a still finer pattern. In order to meet such a demand, the use of exposure light source of shorter wavelength is now studied. For example, a process of forming a finer resist pattern through the use of ArF excimer laser (193 nm in wavelength) or the quintuple harmonic of YAG laser (218 nm in wavelength) has been developed. With the use of such a light source, it has become possible to narrow the minimum line width of wiring pattern down to the order of submicrons. However, studies for forming such a finer pattern are still continuing.
In view of effectively performing a fine patterning process, a development of a resist material which is excellent in dry etch resistance in the step of forming a wiring pattern is now demanded.
In this connection, there has been known to use a photosensitive composition comprising an aromatic compound as a resist material. As for this type of resist material, various kinds of resist materials containing as a base material phenol resin have been developed. However, when this conventional type of resist material is used in a patterning process utilizing as an exposure light source a light of short wavelength as mentioned above, it is impossible, because of its high light absorption, to allow the exposure light to reach deep enough to a required portion remote from the surface of the resist film. As a result, it has been very difficult to form a fine pattern with this conventional resist material, thereby raising a problem.
On the other hand, there has been studied to use polymethylmethacrylate (PMMA) having no aromatic ring since the resin is low in light absorption. However, the resins of this type are accompanied with a problem that they are poor in dry etch resistance.
As explained above, there has been demanded, in order to realize a fine pattern of the order of submicron, to develop a photosensitive material which is low in light absorption and has a sufficient dry etch resistance.